Walker delivered a standout performance on stage in Las Vegas, finishing ahead of Samson Dauda and defending champion Derek Lunsford.
The victory marks a major turnaround for Walker, who finished sixth at the 2025 Mr Olympia.
His improved physique and stage presentation impressed the judges as he emerged at the top of a highly competitive final.
For his victory, Walker takes home the top prize of US$600,000, while Dauda receives US$200,000 for second place and Lunsford earns US$100,000 for third.
Walker also received the People's Champion Award, adding another honour to a memorable night.
The win gives Walker his first Mr Olympia title and the coveted Sandow Trophy, cementing one of the biggest comebacks of the 2026 bodybuilding season.
